What symbols/characters are not allowed in tags?


On the sidebar it says that these are the Tag Characters:

Tag characters: [a-z 0-9 + # - .]

I'd assume anything not listed there is invalid.

  • Do you know what happens when you assume? Sep 18 '09 at 17:25
  • 1
    You get struck by lightning?
    – Randell
    Sep 18 '09 at 17:26
  • 14
    You split assume into an array by substring index 0,3 3,1 4,2 Sep 18 '09 at 17:29
  • It's worth noting that + is only allowed at the end of a tag name.
    – Stevoisiak
    Jul 20 '17 at 2:12

What characters are allowed in tag names?

Always allowed

  • lowercase Latin letters a to z
  • digits 0 to 9

Conditionally allowed

Related Questions

  • You say "single plus allowed at the end of tags" then list tags with two at the end
    – Cai
    Jul 28 '17 at 20:15
  • @Cai Good catch. I've provided better examples
    – Stevoisiak
    Jul 28 '17 at 20:20

At least for chat room tags I was just able to create a tag español for the Spanish chat room. I thought the system would automatically change it to espanol like it does for the question tags. So I went further and tried to create a 日本語 for the Japanese chat room, but it got converted to ???.

So the answer may be:

  • Some Latin-1 characters are no longer disallowed


  • That subsets of characters not allowed in question tags is different to that not allowed in chat room tags


  • There's a bug in chat room tags that allows you to use characters that are not supposed to be allowed

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .